hdu 1724 Ellipse simpson积分

/*hdu 1724 Ellipse simpson积分求椭圆的部分面积simpson积分法 http://zh.wikipedia.org/zh-tw/%E8%BE%9B%E6%99%AE%E6%A3%AE%E7%A7%AF%E5%88%86%E6%B3%95*/#include<stdio.h>#include<math.h>const double eps=1e-8;inline double jue(double a){return a>0?a:-a;}int dbcmp(double a){if(a>eps)return 1;if(a<(-eps)) return -1;return 0;}template<typename T>inline T sqr(T d){return d*d;}double a,b;inline double func(double x){return 2*b*sqrt(1-sqr(x)/sqr(a));}double simpson(double l,double r){return (func(l)+func(r)+4*func((l+r)/2))/6*(r-l);}double work(double l,double r){double mid=(l+r)/2;double ans=simpson(l,r);if(dbcmp(ans-simpson(l,mid)-simpson(mid,r))==0){return ans;}else{return work(l,mid)+work(mid,r);}}int main(){int n;double l,r;scanf("%d",&n);while(n--){scanf("%lf%lf%lf%lf",&a,&b,&l,&r);double ret=work(l,r);printf("%.3f\n",ret);}return 0;}